1. 2.3.2 the strong nuclear force

2. The problem
If you consider that the nucleus of all atoms except hydrogen contain more than one proton, and each proton carries a positive charge, then why would the nuclei of these atoms stay together? The protons must feel a repulsive force from the other neighboring protons.

3. Electrostatic repulsion
Substitute values for 2 protons and calculate the repulsive force between them

4. Gravitational attraction,
Gravitational attraction
Gravity could be holding the nucleons together but must be greater than the electrostatic repulsion between them.
Substitute values for 2 protons to calculate the size of the gravitational force. Could this be the answer?

5. The Strong Nuclear Force
Also referred to as the strong force.
Is one of the four basic forces in nature (the others being gravity, the electromagnetic force, and the weak nuclear force).
As its name implies, it is the strongest of the four. However, it also has the shortest range, meaning that particles must be extremely close before its effects are felt.
Its main job is to hold together the subatomic particles of the nucleus (protons, which carry a positive charge, and neutrons, which carry no charge. These particles are collectively called nucleons).

6. The strong nuclear force is created between nucleons by the exchange of particles called mesons. This exchange can be likened to constantly hitting a ping-pong ball or a tennis ball back and forth between two people. As long as this meson exchange can happen, the strong force is able to hold the participating nucleons together.

7. Nucleons must be extremely close together in order for this exchange to happen.
The distance required is about the diameter of a proton or a neutron.
If a proton or neutron can get closer than this distance to another nucleon, the exchange of mesons can occur, and the particles will stick to each other.
If they can't get that close, the strong force is too weak to make them stick together, and other competing forces (usually the electromagnetic force) can influence the particles to move apart.

8. Another problem
If the strong force was only an attractive force though, the nucleons would collapse in on themselves.
Therefore when the nucleons are REALLY close together, it must become a repulsive force.

10. existing 2 protons cannot exist without a neutron and vice versa.
Both particles are needed for a stable nucleus.
Due to the 0 charge of a neutron, the net force on it will always be the strong force.
The resultant force on a proton will be the vector sum of the electrical and strong forces.

11. equilibrium
If any nucleon is in equilibrium the forces on it must be balanced.
As neutrons only feel the strong force, they must be at a distance of approximately 2.4x10-15 m. If they were further apart, the strong force would pull them closer together again.
For 2 protons, the electrical force of repulsion must be balanced by the attraction of the strong force, which results in similar distances between the protons.